docs: remove `VirtualMachineInstanceConfig`
docs: remove `VirtualMachineInstanceConfig`

This CRD was actually implemented as the `VM` type, and is documented
in [0].

[0] - https://kubevirt.io/user-guide/architecture/#virtualmachine

Signed-off-by: Miguel Duarte Barroso <c798d3f0e4fda7badfc3bbd91babde7ebd48b6c2@redhat.com>

kubevirt/kubevirt,kubevirt/kubevirt,kubevirt/kubevirt,kubevirt/kubevirt